Length Tool
How to set up the Length tool:
// Init cornerstone tools
cornerstoneTools.init();
// Enable any elements, and display images
// ...
// Add our tool, and set it's mode
const LengthTool = cornerstoneTools.LengthTool;
cornerstoneTools.addTool(LengthTool)
cornerstoneTools.setToolActive('Length', { mouseButtonMask: 1 })